title: Synthesis and use of radio cobaltic EDTA as an extracellular marker in rabbit heart.
abstract: A new gamma-labeled marker for extracellular space is the cobaltic form of 58Co-ethylenediaminetetraacetic acid (58Co-EDTA). The cobaltic ion has a much higher affinity for EDTA than the cobaltous ion; it is prepared as a potassium salt, K+(58Co3+-EDTA4-), and is apparently biologically inert. Testing by equilibration in intact rabbits and comparing the myocardial content with that of [14C]sucrose give values of the volume of distribution in the myocardium of 0.294 +/- 0.052 ml/g for 58Co-EDTA and 0.303 +/- 0.051 ml/g for [14C]sucrose (SD, n = 130, for two hearts), with the ratios of 58Co-EDTA/sucrose averaging 0.973 +/- 0.043 (n = 130). The average value of the extracellular fluid measured in isolated rabbit interventricular septum using Co-EDTA was 0.51 +/- 0.05 ml/g (SD, n = 16) and 0.46 +/- 0.04 ml/g using [14C]sucrose as an extracellular fluid space (ECF) marker. Flushing with a high concentration of nontracer Co-EDTA does not reveal any release from binding sites. The gamma-energy (811 KeV), long half-life (71.4 days), stability, and lack of binding to tissue components make 58Co-EDTA a useful marker for ECF.
mesh_terms: D000818:Animals; D001692:Biological Transport; D002250:Carbon Radioisotopes; D002614:Chelating Agents / Q000138:chemical synthesis*; D003037:Cobalt Radioisotopes; D004492:Edetic Acid / Q000138:chemical synthesis*; D005110:Extracellular Space / Q000032:analysis*; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000032:analysis*; D011817:Rabbits; D011865:Radioisotope Dilution Technique; D013395:Sucrose
chemical_list: D002250:Carbon Radioisotopes; D002614:Chelating Agents; D003037:Cobalt Radioisotopes; C028222:cobalt-ethylenediamine tetraacetic acid chelate; D013395:Sucrose; D004492:Edetic Acid